CO₂ Technology Centre Mongstad – Design, Functionality and Emissions of the Amine Plant (2011)

Gelein de Koeijer^*a, Yngvil Enge^a, Knut Sanden^b, Oscar Fr. Graff^b, Olav Falk-Pedersen^c, Tore Amundsen^c, Sverre Overå^a

^a Statoil ASA, N-4035, Stavanger, Norway ^b Aker Clean Carbon N-0212, Oslo, Norway ^c TCM DA, NO-5954 Mongstad, Norway

Abstract

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The CO₂ Technology Centre Mongstad (TCM) project is constructing two large post-combustion CO₂ capture demonstration plants near the Statoil operated Mongstad refinery, located at the Norwegian west coast north of Bergen. TCM’s partners are Gassnova, Statoil, Sasol and Norske Shell. This paper describes the amine plant. The amine plant is designed and constructed by the CO₂ capture technology provider Aker Clean Carbon (ACC) with specifications and additional generic functionalities defined by TCM. Several new technology elements will be tested and verified, including improved solvents. Monoethanolamine and a new ACC solvent will be tested during the initial 16 months of operations. Thereafter tests will be run by the TCM partners. The quality and quantity of the emissions from the absorber to air have become top priority. Currently they represent a health and environmental uncertainty, mainly due to the lack of reliable and accessible experimental data. While knowledge and experience of these emissions are rapidly increasing, an emission permit is being applied for. The amine plant is highly flexible and can combine several novel technologies. Due to its scale it will give valuable information on utility and space requirements, scale-up properties and contribute to reducing HSE risks and costs.

1.  Introduction

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The CO₂ Technology Centre Mongstad (TCM) project [1,2] is constructing two post-combustion CO₂ capture test plants near the Statoil operated Mongstad refinery, situated at the Norwegian west coast north of Bergen. One unit will use  amine  technology and the other chilled ammonia technology. TCM’s partners are Gassnova (75,12% – representing the Norwegian State), Statoil (20%), Norske Shell (2.44%) and Sasol (2.44%). Statoil is the operator for the execution phase and has been selected as the operational service provider. The overall aims for TCM are:

• Test, verify and demonstrate CO₂ capture technology owned and marketed by vendors
• Reduce cost, technical, environmental and financial risks
• Encourage the development of a market for such technology
• International deployment

At the moment of writing, this project is one of the largest CO₂ capture demonstration units under construction. It is highly flexible in order to obtain information about different CO₂ capture technologies. The amine plant is designed and constructed by the CO₂ capture technology provider Aker Clean Carbon (ACC) [3]. The plant is under construction (see Figures 1, 2 and 3) and start-up is scheduled for 2011. The selected ACC’s Advanced Carbon Capture Process [4] includes several special new features such as:

• New improved amines, which exhibit less degradation and reduce energy demand
• Emission control system, which gives minimum emission to air
• Rectangular concrete absorber with internal liner
• Energy saver, which reduces the steam demand
• Two desorbers with alternative reboiler designs
• Thermal reclaimer design, which gives minimum waste

TCM will be a driving force in the qualification of large-scale capture technology and development of improved technology. The aim of this paper is to describe the design and functionality of the amine unit, and to contribute to the international  deployment of TCM.

2.  Method of design

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The concept for the amine plant was defined through an industrial stage-wise development, which started summer 2007. International competition between technology suppliers was used. The criteria for the competition were based on fulfilling TCM’s aims. A pre-qualification process reduced the number of suppliers. After a bidding round based   on Front End Engineering & Design (FEED) studies, Aker Clean  Carbon (ACC) was chosen for the detailed design  and  construction early 2009. The basis for design is ACC’s amine based CO₂ capture technology developed over the last years [3,4,5] but adapted to specifications, functionalities and flexibility requirements  defined  by the TCM project. Several new technology elements will be tested and verified in the plant, including improved solvents.

An important design strategy has been to utilize the same  construction methods for the TCM plant as will be utilized for full scale plants. This can be exemplified by the absorber that has been slip formed, which is a great advantage for large constructions. Figure 2 shows the slip formed absorber at the Mongstad site. Another example  is that the plant has been extensively modularized in order  to prefabricate off-site. Figure 3 shows the construction of one of the reboilers on a pre-assembled unit at the Aker Stord yard, south of Bergen. This serves two main benefits; the productivity is generally greater at fabrication yards than site, and it is a risk reducing measure to minimize construction work close to complex sites as the Mongstad refinery.

3.  Design and Functionality

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3.1 Overall design

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By fulfilling TCM’s aims  specifically for the amine unit, the design has become one of the most advanced ones for amine plants with a high degree of flexibility. The process is an absorption/desorption process [3] and the overall design is shown by a 3D illustration in Figure 4.

The most important characteristic of the TCM facility is high flue gas flexibility by being able to capture CO₂ from two different flue gas sources. This is a unique feature relative to other pilot and demonstration units of this size. The first flue gas is a slip stream from gas fired combined heat and power (CHP) flue gas with 3,5 vol-% CO₂. This flue gas is representative of gas fired power plants. When using this flue gas the amine  unit will have a capacity of 25 000 tonnes CO₂/yr captured. The second flue gas is a slip stream from Residue Fluid Catalytic Cracker (RFCC) flue gas with 12,9 vol-% CO₂.

This flue gas is representative of refineries, and also for coal fired power plants since it contains similar levels of SO_x, NO_x and particulates. When using this flue gas the amine unit will have a capacity of 74 000 tonnes CO₂/yr captured. The unit is designed for 85% CO₂ capture rate with CO₂ purity of 99,9% for both CHP and RFCC flue gases. Furthermore,  it  will  be possible to recycle captured CO₂ to the CHP flue gas to achieve concentrations between 3,5 and 9% CO₂ in the CHP flue gas.   This will enable to test the effects of Exhaust Gas Recycle (EGR) [6] on amine based CO₂ capture. The critical areas of interest  for the technology include determining solvent degradation and process energy demand.

It will be possible to operate with large turn-downs. The design specification is 50% for both flue gasses which means a possible range of 16–100% for the CO₂ product rate. Turn-down behaviour is especially important for quantifying load following capabilities and general flexibility. Relative to other capture technologies of pre-combustion and oxyfuel, this flexibility is said to be one of the important advantages of post-combustion [7]. The most interesting issues to be studied are the liquid distributor capacity and the vapour/liquid distributions in the packings.

Further, the flue gas treatment system upstream of the absorber allows for control and adjustment of flue gas temperature and water content. This allows the absorber inlet to be operated from 25 °C and up to more than 50 °C.

The utilities (steam and electricity) and tie-ins (ducts, blowers, flue gas coolers) are designed for 120% capacity to be able to test plant limitations. Normal design of CO₂ capture units contains design margins. Currently these design margins have an uncertainty in the same range as the best available models. This uncertainty is estimated to be 10-20% [8]. Control of design margins is important for designing with minimum investment cost.

CO₂ compression and storage is not included at this stage but may be added in a later phase.

3.2 Sampling, measurement and analysis

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Being a demonstration unit where knowledge is the main product, extensive analyzers and monitoring instruments for measuring the improvements with high accuracy will be installed. The most important variables will be measured online where possible. The design includes many manual sampling points in order to be able to perform more detailed analyses. Special focus has been on emissions to air from the absorber (see Ch.4). It will be possible to fully define and where possible over-define the mass and energy balances in the unit in order to verify simulation models. In the absorber outlet and CO₂ product temperature, pressure, flow, composition (CO₂, N₂, O₂, Ar, H₂O, NO_x, SO_x, amines, NH₃, some degradation  products)  will be measured  online. Corrosion coupons spool pieces are being installed to evaluate the use of other desorber, absorber, heat exchanger and piping construction materials than the ones used.

3.3 Solvents

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The plant is designed to be able to test different solvents. ACC has scheduled to test the following:

• 30 wt% MEA (monoethanolamine) solution for 4 months, which is a well known solvent [9, 10]. The performance guarantees from ACC are based on this solvent. The results will give a benchmark for the novel solvents.
• improved solvent which contains mixtures of primary, secondary and tertiary amines developed by ACC and partners 

The solvents will be tested both on RFCC and CHP flue gas. The improved solvent has demonstrated low degradation and  reduced reboiler duty in tests at a coal-fired power station in Scotland (ref. section 3.6). A test program will be set up for   obtaining best possible data, knowledge and experience.

3.4 Absorber

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The absorber has a unique design and flexibility, see also  Figure 5. The design philosophy from TCM was that it should   enable testing of most amine based technologies. ACC has designed the absorber together with Koch-Glitsch as packing supplier. The CO₂ absorption part has three packing sections for enabling 85% CO₂ capture with slow and fast amines from RFCC, CHP flue gas and CO₂-enriched CHP flue gas. The lowest section is the tallest one with two  shorter sections above it of similar  heights. Lean amine can be fed at the top of each section, but only above one section at a time.

The absorber design is part of ACC’s technology. The outer wall is rectangular (internal dimensions: 3,5x2x62 m) made of concrete with internal polymer lining. TCM will have the first lined concrete absorber in the world for CO₂ capture from flue gasses with amines. The wall is slip formed with the liner continuously installed during the slip forming. The wall is penetrated extensively  for  various inlets, outlets, sampling points and online measurement instrumentation. The pressure drops will be measured over each packed section and the temperature will be measured every rising meter at a grid of horizontal locations. The outlet of the absorber is a conventional circular pipe (1 m diameter, 4 m height) with various penetrations for online Fourier transform infrared (FTIR) spectroscopy concentration measurement and iso-kinetic sampling. The flue gas inlet is designed with the aid of computational fluid dynamics to ensure proper gas distribution.

The wash section consists of water wash packings with demisters above and below. The water wash is designed such that ACC’s novel emission control system can be tested. There is a possibility of installing additional demisters. Relative to normal practice, this section may seem overdesigned. The reason is to quantify the emissions to air by experimenting with various washing configurations. This will contribute to reducing the residual health & environmental risk to an acceptable level.

The division of CO₂ absorption sections can be modified in the future. The lowest tallest section can be divided into two.the section improve the liquid/vapour distribution. Moreover, each  of the 3 sections has a possibility of 10% increase in packing heights by adding  extra  height  between liquid distributor and packing section.

By the addition of extra inlets, internal brackets and other provisions of extra distributors, it is also possible to add  an  intermediate heat exchanger at two different heights.

3.5 Desorbers and Reclaimer

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TCM’s amine unit has two strippers or desorbers, enabling operation with minimum energy demand with both flue gases. Moreover two desorbers are needed to meet the turn-down requirements. ACC has designed the desorbers using Koch-Glitsch as packing supplier. The diameter of the RFCC desorber is 2,2 m and for the CHP desorber 1,2 m. Both desorbers have one packed section for CO₂ desorption and one for water wash above the rich amine inlet. Height is reserved and penetrations are made for   the possibility to split the CO₂ desorption section for future installation of split flow and/or better vapour/liquid distribution. The pressure in the desorbers can be increased and reduced. Pressure variation tests can reveal the optimum compromise between steam demand, steam quality, compressor requirement and degradation for each solvent and flue gas.

Each desorber has its own reboiler which is designed for current scheduled operation. Each desorber can be fitted with  a  second reboiler in case another type of operation is decided, or new or optimized types of reboilers are developed.

The RFCC desorber has installed ACC’s technology for recovering energy in pressurized hot lean amine [3]. The CHP  desorber does not have such an Energy Saver, but provisions are made for future installation. The Energy Saver converts low  value energy into useful stripping energy and includes heat integration. This Energy Saver requires more electricity  but  less steam, and leads overall to reduced energy demand.

The reclaimer will be a thermal reclaimer with external steam heating. It will be used initially for getting data and experience, which is  scarce for reclaiming. It is possible to upgrade the current  reclaimer for reduced pressures. Valves are installed and  place is reserved for a future 2nd reclaimer with improved technology.

3.6 Mobile test unit

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In the initial period of operations, ACC’s Mobile Test Unit (MTU) will be installed at the Mongstad site, and will be used for tests in parallel to the larger unit. It has an absorber diameter of 0,4 m, a height of 25 m, and a capture capacity of 0,2 t CO2/hr on flue gas from coal fired power plants. It has been operated in Risavika Gas Centre (Norway) on flue gas from a gas turbine and in Longannet (Scotland) on flue gas from a coal fired power plant as part of the SOLVit R&D project [5]. It will be used to gain early test results and experience from operation on two different flue gas sources with new amines. However, such tests lack the large-scale effects and some of the flexibility of the larger scale unit. The combination of results from both units will be synergetic.

4.  Emissions to Air

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The quality and quantity of the emissions to air have become top priority. Currently they represent a health and environmental uncertainty, mainly due to the lack of reliable and accessible experimental data. A new emission control system will be tested in the TCM amine absorber. The system has the potential to reduce the emission of amines and degradation products to a minimum. A large part of the efforts in this project went into assessing the assumptions on the formation, dispersion and acceptance criteria of carcinogenic nitrosamines. Nitrosamines are assumed to be formed from reactions between secondary/tertiary amines and NO_x, both in the absorber and in the atmosphere. There are several, major uncertainties in the selected nitrosamine assumptions, such as formation time and conditions, stability, and resulting concentration levels in the plant and surroundings. Formation of nitrosamines has been experimentally observed in laboratory experiments [10]. New knowledge is being rapidly generated and various experiments are being executed [10, 11, 12, 13]. In this continuously changing situation, TCM is applying for an emission permit to the Norwegian authorities in the summer of 2010 [13]. This application is the world’s first application for a larger scale amine unit that addresses the emissions in detail, and can be considered as pioneering work. In short, the procedure of writing this permit consisted of obtaining:

• The best possible estimates of the emissions from ACC, i.e. an environmental budget. Qualitative measurements, analogies and theory were used for estimating the emissions. The estimates were given in the form of scenarios in order to capture the whole range of operations, including high values during upsets and low values which are expected from theoretical calculations. As an example, the estimates for two scenarios (expected and design) for MEA for CHP and RFCC flue gasses are given in Table 1 for three of the main emitted components. The expected values are the most likely ones normal operation will be below. The design values are those used for the design described earlier in this paper. As can be seen in the Table, the design values are already conservative relative to the expected values. The estimates are based from measurements at the MTU. Other components that have been observed in the measurements from the MTU are formaldehyde, methylamine, ethylamine, dimethylamine, formic acid, acetic acid, butyric acid, propionic acid, n-(2-hydroxyethyl)imidazole, n-(2- hydroxyethyl)-formamide and nitrosamines as a group. In addition, it is likely that ketones, amides and other secondary  amines will be present.

• Health, safety and environmental data on all amines and their degradation products, i.e. biodegradability, ecotoxicity, acute toxicity, mutagenicity, reproduction toxicity, irritation/corrosion, sensitation, repeated dose toxicity. ACC used SINTEF as consultant for this work, including searching the International Uniform ChemicaL Information Database (IUCLID), the ECOTOX database of the US Environmental Protection Agency (EPA), the BIODEG database of the Syracuse Research  Centre (SRC), and the GENETOX database (EPA). Data for all components need to be collected, even if the amine or its degradation product is non-volatile giving negligible emissions. Operators can still come into contact with it during operations like reclaiming, filter change, sampling etc.
• Acceptance criteria and exposure limits for all amines and their degradation products in air and drinking water by searching

Norwegian and international HSE regulations and using the new REACH regulation from the European Union.

• Dispersion modelling results for all amines and their degradation products in air and drinking water. This work was done by Norwegian Institute for Air Research (NILU) and used input from all previous activities.

Due to the mentioned uncertainty the precautionary and worst case principles have been used actively, which has lead to the  use of several assumptions. An important assumption is on how much of the emitted amine reacts with NO_x in the atmosphere to nitrosamines. It is assumed that 2-10% of all emitted secondary and tertiary amines are transformed instantaneously into nitrosamines [13]. It is further assumed that the formed nitrosamines are 100% stable in the atmosphere and will not decrease.  This is a precautionary approach which is recommended at this stage. R&D on this assumption has started [13] but there is still little published experimental and theoretical evidence. As yet, Norway does not have acceptance criteria for nitrosamines in air  and drinking water. Hence, information from outside Norway had to be assessed. It was decided to use the criteria from the nitrosamine with the lowest concentrations found in EPA/IRIS for all nitrosamines, i.e. a group approach. These were found for N-nitrosodimethylamine, and are 0.07 ng/m3 for air 0.7 ng/l for drinking water [14].

After the data gathering and modelling an application was written for certain emission rates that satisfy the acceptance criteria. Such rates are meant to give flexibility for performing the desirable tests. Hence, they are not actually measured rates but aggregated numbers with contingencies. It is expected that new knowledge will elucidate the validity and level of conservatism    of the numbers and assumptions in the application. However, they are considered to be the most valid ones with current available knowledge. For other future applications of these assumptions it is recommend to critically re-assess them with the most recent knowledge.

5. Technology Qualification

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A structured technology qualification program is being executed for reducing the technology risks to an acceptable level for such a demonstration unit. The work consisted of making a qualification basis, technology assessment, failure mode identification and risk ranking, and selection of qualification methods. The technology qualification program has been designed by ACC with DNV as consultant, and has followed a specific procedure for CO₂ capture presented in earlier published work by DNV [15]. These guidelines were developed in an R&D Joint Industry Project (with Aker Solutions, Aker Clean Carbon, Statoil, Statkraft, and DNV as partners). They are now used in an industrial environment for the first time. The detailed results are an important part of ACC’s competitive knowledge. The main technology risks were related to the emissions to air  and  absorber construction and functionality. Hence, the ongoing execution of the qualification methods is mainly focused on reducing these risks. A good example is the construction of a mock-up of the slip forming platform for the absorber, see  Figure 6. With this mock-up the slip forming technology was tested before it was used in spring 2010 for the actual absorber.

This mock-up has contributed to the 62 m high concrete absorber being successfully raised within 20 days by the tested slip forming method.

6. Conclusions

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An amine demonstration unit is being constructed at the CO₂ Technology Centre Mongstad, located north of the city of    Bergen in Norway. At the moment of writing, this unit will be one of the largest demonstration units for experimenting with  amine technology. The design is highly flexible with an absorber with multiple sections and two desorbers with different diameters. Ample provisions for future improvements are also included. The unit  can  capture  flue gasses representative of gas and coal fired power plants, as well as petrochemical plants and refineries. The technology supplier is Aker Clean Carbon and several new design features will be tested. Due to its scale it will give valuable information on utility and space requirements, scale-up properties and contribute to reducing HSE risks and costs. 30 wt% MEA and a new solvent developed by ACC and partners will be tested during the initial 16 months of operations. Subsequent testing will be done by the TCM partners. Construction technologies that may reduce construction cost of large scale units are also included. In parallel a much smaller Mobile Test Unit will be used for faster and cheaper tests that can benefit the test at the larger unit.

The quality and quantity of the emissions to air have become top priority. Currently they represent a health and environmental uncertainty, mainly due to the lack of reliable and accessible experimental data. New knowledge is being rapidly generated and various experiments are being executed. In this continuously changing situation, TCM is applying for an emission permit to the Norwegian authorities. It is expected that new knowledge will elucidate the validity and level of conservatism of the numbers    and assumptions in the application. However, they are considered to be the most valid ones with current available knowledge.

Another novelty in this project is the use of recently developed guidelines for technology qualification of CO₂ capture technology.

7.  References

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1. De Koeijer GM, Enge YO, Thebault C, Berg S, Lindland J, Overå SJ. European CO₂ Test Centre Mongstad –Testing, verification and demonstration of post-combustion technologies, Energy Procedia 2009;1:1321-1326
2. Website on CO₂ Technology Centre Mongstad www.tcmda.com (accessed July 2010)
3. Aker Clean Carbon website, www.akercleancarbon.com (accessed July 2010)
4. Oscar Fr. Graff, European CO₂ Technology Centre Mongstad – Advanced Amine Carbon Capture Plant, Trondheim CCS-5 international conference 2009, http://www.energy.sintef.no/arr/CO2_2009/Presentations/B3-3.pdf (accessed July 2010)
5. Website on SOLVit program, http://www.akercleancarbon.com/section.cfm?path=418,465 (accessed July 2010)
6. ElKady AM, Evulet A, Brand A, Ursin TP, Lynghjem A. Application of Exhaust Gas Recirculation in a DLN F-Class Combustion System for Postcombustion Carbon Capture. J. Eng. Gas Turbines Power 2009;131;3:034505-[7]
7. Lucquiaud M, Chalmers H, Gibbins J. Capture-ready supercritical coal-fired power plants and flexible post-combustion CO₂ capture, Energy Procedia, 2009;1:1411-1418
8. Luo X, Knudsen JN, De Montigny D, Sanpasertparnich T, Idem R, Gelowitz D, Notz R, Hoch S, Hasse H, Lemaire E, Alix P, Tobiesen FA, Juliussen O, Köpcke M, Svendsen HF. Comparison and validation of simulation codes against sixteen sets of data from four different pilot plants. Energy Procedia, 2009;1:1249-1256
9. Knudsen JN, Jensen JN, Vilhelmsen PJ, Biede O, Experience with CO₂ capture from coal flue gas in pilot-scale: Testing of different amine solvents, Energy Procedia, 2009:1;783-790
10. Fostås B, Sjøvoll M, Gangstad A, Nenseter B, Pedersen S, Sørensen AL, The flue gas degradation chemistry of MEA based solvents, Submitted to Proceedings of GHGT-10 Amsterdam Sept 2010
11. Lepaumier H, Da Silva EF, Einbu A, Grimstvedt A, Knudsen JN, Zahlsen K, Svendsen HF, Comparison of MEA degradation in pilot-scale with lab-scale experiments. Submitted to Proceedings of GHGT-10 Amsterdam Sept 2010
12. Website for R&D project “Atmospheric Degradation of Amines” – ADA http://ada.nilu.no/ (accessed July 2010)
13. TCM. Application for emission permit with appendices, to be published on www.klif.no (Norwegian) 2010
14. EPA/IRIS database entry for N-Nitrosodimethylamine, http://www.epa.gov/ncea/iris/subst/0045.htm (accessed July 2010)
15. Myhrvold T, Helle K, Johnsen K, Hussain A. Development of a guideline for the qualification of CO₂ capture technology, Energy Procedia 2009;1:1527-1534

European CO₂ Test Centre Mongstad - Testing, Verification and Demonstration of Post- Combustion Technologies (2009)

Gelein de Koeijer*^b, Yngvil Oftebro Enge^b, Cyril Thebault ^c, Svein Berg^b, Julia Lindland^a, Sverre  Johannesen Overå^b

^aGassnova SF, N -3920 Porsgrunn, Norway ^bStatoilHydro ASA, N-4035, Stavanger, Norway ^cVattenfall AB, SE-162 87 Stockholm, Sweden

Abstract

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The European CO ₂ Test Centre Mongstad project will construct two post-combustion CO₂ capture test plants (amine and chilled ammonia) with total annual CO₂ capacity of 100,000 tones. The ambitions are:

• Develop technologies for CO₂ capture capable of wide national and international deployment
• Reduce cost and technical, envi ronmental and financial risks related to large scale CO₂ capture
• Test, verify and demonstrate CO₂ capture technology owned and marketed by vendors
• Encourage the development of a market for such technology

Both plants will be able to capture CO₂ from two d ifferent flue gases with 3.5 and 12.9 mol% CO₂.

1. Introduction

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On 12 ^th October 2006 Statoil (now StatoilHydro) and the Norwegian State agreed on implementation of CO₂ Capture and Storage (CCS) at the Mongstad refinery  [1].  The Mongstad refinery is located north of  the city  Bergen in Norway. T he refinery is operated by StatoilHydro. In 2010 major improvements of the refinery will be ready including connections to several of its neighboring industrial sites and offshore  platforms.  This  improvement includes the construction of a Combined Heat and P ower plant (CHP) which will add ~1.3 million tonnes CO₂ per year to the emissions to the already existing emissions from the refinery, of which t he Residue Catalytic Cracker (RCC) is the largest contributor with ~0.8 million to nes CO₂ per year. The agreement requires a two-stage implementation of CCS. The first stage is the European CO₂ Test Centre Mongstad (TCM) with a design capacity of 100 000 tonnes of CO₂ /year. The second stage is full scale implementation. The aim of this paper is to describe the tech nical choices and aims of the first stage – TCM.

The purpose of the test centre is to identify, test, develop and qualify CO₂ capture technologies, and to reduce    cost and financial, technical and environmental risk connected to the construction and operati on of a full scale CO₂ capture plant. The ambitions of the TCM project are:

• Develop technologies for CO₂ capture capable of wide national and international deployment
• Reduce cost and technical, environmental and financial risks related to large scale CO₂ capture
• Test, verify and demonstrate CO₂ capture te chnology owned and marketed by vendors
• Encourage the development of a market for such technology

The TCM partners are Gassnova SF (representing the Norwegian State), DONG Energy, Shell, StatoilHydro, and Vattenfall. The partners are operators from both oil&gas and power industry, and participate actively in the developmentof CO₂ Capture and Storage.

2. Technology Assessment

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Many technologies for CO₂ capture are documented [2], and groups of these technologies have previously been assessed on various bases , see e.g . Steeneveldt et al [3] and CO₂ Capture Project (CCP) [ 5]. At the start of the TCM project these technologies needed to be assessed with TCM specific demands enabling a technology choice. T he following criteri a were used together with the knowledge from the partners:

• Extent of modification and disturbances to the CHP and refinery. The operation of TCM (and the later full scale capture plant ) should not require any modifications to the CHP plant and refinery, nor disturb their operations
• Usefulness and improvement potential for the large-scale Mongstad CO₂ capture plant
• General improvement potential relative to MEA based post -combustion (as documented by e.g. IEA [ 4] and CCP [ 5])
• Availability of established and emerging suppliers for the TCM project
• Technology demonstration and qualification aims of TCM in relat ion to its maturity. TCM should preferably demonstrate and qualify new and most probably immature technology.
• CO₂ capture plant at Mongstad will have no harmful emissions in accordance  to  the  zero  harmful emission target of the Norwegian authorities and the Mongstad emission permit
• The possibility to capture CO₂ fromthe high CO₂ content flue gas from the RCC addition to CHP

The result was to recommend improved amine and c hilled ammonia technology. Amine  technology  is  w ell known, simple and flexible, but still has improvement potential on steam demand, cost,  emissions,  discharges, solvent formulations, materials/ corrosion,  and scale-up. An important reference was the Esbjerg pilot unit [6], which is the largest amine based post -combustion pilot unit in the world with a 1 to n CO₂ per capacity and 1 m diameter absorber. The chilled ammonia technology uses the general absorption/desorption based on a carbonate/bicarbonat e cycle :

CO₂(g) + CO₃^2-(aq/s) + H₂O (l) Û 2HCO₃^– (aq/s)

The reaction needs a cation for which the supplier Alstom has chosen ammonium. Alstom is developing this technology and calls it the ‘Chilled Ammonia Process’ (CAP) [7]. Its possible advantages  are  reduced  energy demand, fewer CO₂ compressor stages, well known low cost chemicals, and reduced amount of waste . However this technology is unproven, has few available experimental data, need s extensive cooling,  and  requires  handling of slurries and ammoni a. The chilled ammonia technology h as been tested less and therefore represents a higher risk.

3. Overall Concept and Functional Requirements

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Figure 1 shows the TCM overall concept and design capa cities  based on the main functional requirements agreed in the early phase of the project. Each of t he two CO₂ capture technologies (Amine / C hilled Ammo ni a) shall be able to capture CO₂ from two different flue gas sources (CHP/RCC) and shall operate independent of each other . The CHP flue gas represents a gas fired  power  plant with 3.5 mol% and the RCC flue gas represents coal fired power  plant with 12.9 mol% with particulates, SO_x and NO_x.

The design capacity will be 100 000 t ones CO₂/yr if both technologies operate simultaneously with > 85% CO₂ capture efficiency and 92% regularity. It will be possibl e to simulate the effects on CO₂ capture of gas  turbine Exhaust Gas Recycling (EGR ) by CO₂ recycle from either plant back to the CHP flue gas . EGR is a technology for increasing the CO₂ concentration to ~4-8 mol% and reduce the flue gas volume from gas fired turbines, see e.g. CCP [5]. The technologies need to have high flue gas flexibility in each CO₂ capture  unit  for handling both CHP and RCC flue gas. The plants will be designed such that  scale-up to full-scale plant can be done based on the results from TCM. The amine technology has different gas flows through the absorber for RCC and CHP exhaust, while carbonate has the same. The reason was that the carbonate absorber performance was estimated to  be less sensitive   for CO₂ concentration than amine. The maximum flue gas flows from the sources are 20-34% too large relative to what is estimated needed in the capture process. This will give flexibility and the ability  to test the limits. Their sizes ar e chosen by a compromise between this flexibility and duct/tie-in cost.

Further, since the ambition for TCM is to create a centre for testing of post -combustion CO₂ capture technologies and associated facilities, the TCM project includes access to flue gas es, utilities and captured CO₂, as well as additional space reserved for testing of new (future) equipment and technologies in smaller or similar scale as the initial two technologies. CO₂ compression and storage is not included at this stage but may be added in a later phase. The sizes of these plants will be significantly larger than the existing pilot plants. The absorber diameters will be expected to be around 2.5 -4.0m, while their heights may be 40-60m. Relative to the Esbjerg unit a scale-up factor of 5-10 will reached. It is expected that this size increase will be an important contribution in the scale -up of post-combustion CO₂ capture.

4. Test objectives

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The overall test objectives are:

• Demonstrate/quali fy and scale-up of high risk technologies (Chilled ammonia)
• Achieve incremental technology improvem ents in a generic and flexible a mine test unit
• Build and share knowledge and competence of CO₂ capture technology among th e partners for full -scale realization
• Construct a test plant for CO₂ capture tech nology applicable for both gas- and coal-fired power stations, balancing and taking into account the needs (application, geography) of the individual partners
• Measure and compare test results against reference cases to achieve the strategic ambitions
• Obtain good relations to vendors of CO₂ capture technology and understand their offerings and capabilities

5. Design of Amine Plant

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This chapter describes the main specific test objectives and functionality requirements for the amine plant.

HSE: Main HSE issues identified are the emissions and discharges of the solvents used , i.e. main amines, degradation products, activators, inhibitors, anti -foams, metals/metaloxides, SO _x, and NO_x. Technology and equipment that avoid these emissio ns will be included as far as reasonably possible for a test plant. Sampling, measurement and analysis methods and tools will be documented and tested for use before the start-up. U se and production of environmentally harmful chemicals need to be minimized during design.

Equipment: The pl ant will consist of one flexible absorber and two strippers for enabling CO₂ capture from both RCC and CHP gas. One stripper will be designed for CHP exhaust and one for the RCC exhaust.   Moreover, it will   be used for testing of different solvents, requiring a high flexibility of operating parameters and filling/emptying capabilities. Verification of reduced h eat and electricity demand is of high priority. In order to have flexibility in future improvements, s pace will be allocated for:

• Inter-stage abso rber cooling
• Split flow from both strippers
• Additional reclaimer
• Additional reboilers in both strippers
• First stage of  CO₂ compression train

Nozzles and space have been allocated to allow testing of new or alternative equipment components within the initial plant.

The plant will allow for accurate measurement of temperatures, pressures, flows and composition.  Mat erials testing test facilities for other steel qualities, concrete, coated mater ials and plastic will be installed . Multiple temperature and pressure measurement devices in absorber and stripper will be installed. Measurement of the amine and other chemicals in the entrained washing water will be possible. It shall be possible to  measure the  impact of SO₂, NO_x, particles, iron oxides and chlorides on the amine plant performance (e.g. amine degradation rate, filtration rate, corrosion rate, etc.)

Absorber : The absorber will have at least three sections of packing for CO₂ removal complete with liquid distributors and liquid draw trays:

• The height of t he lowest bed is determined by the performance of a fast amine with RCC flue gas
• The second height is determined by the performance of a fast amine with CHP flue gas and of a slow amine with RCC flue gas. In case these heights significantly differ a fourth section can be included
• The third height is determined by the performance of a slow amine with CHP flue gas.

It will be possible to replace the packing/packing material with other packing type and other packing materials,

i.e. structured, random and plast ic. Below a demister, two water wash sections will be installed in the top of the absorber with minimum water consumption as design criterion. Space for a second demister will be allowed for.

Strippers : The two strippers will have at least two sections o f packings with nozzles and brackets to enable installation of liquid distributors and liquid draw trays for split flow operation. It will  be  possible  to  take  out packing. The energy contained in the pressurized hot lean amine leaving the RCC -stripper will be utilized  for reducing overall energy demand of the plant when capturing CO₂ from the RCC gas. It will be possible to run the RCC-stripper without this technology.

Testing ranges: It will be possible to operate with CO₂ concentrations in flue gas from 3.5 -12.9 mol% with minimum steam conditions at 100% load and 50% turndown for qualification for large-scale  operation  by  utilizing the flexibility provided by multiple absorber sections and two strippers. Testing of RCC flue gas will be possible at varying of SO₂ conc entrations. It is aimed to have a long term test at stable high SO₂ concentrations.  It will be possible to test different solvents.

An extensive test and development program will be prep ared utilizing the available  functionalities  before  start-up.

6.    Design of Chilled Ammonia Plant

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The Chilled Ammonia Process (CAP) is currently being developed and commercialized by Alstom.  The  technology is ne w and the first pilot plant with continuou s operation of integrated absorber and regenerator was started 2008 at WE Energies coal fired power plant in Wisconsin , USA  [8 ]. Figure  2 shows a 3D sketch of the CAP at TCM as envisaged by Alstom.

Chemistry and heat integration in the CAP are more complex compared to other commercially available CO₂ capture technologies. There will be precipitation of ammonium bicarbonate, e.g. a mixture of solid particles of bicarbonate and the liquid solvent will form a slurry. Solids have thus to be handled during process operation. However, amm onium bicarbonate will  dissolve  during heating of the solvent in the lean/rich heat exchanger and in the regenerator, which operates at high pressure. Ammonia  in  water  is volatile, and special measures h ave to be  taken to avoid excessive emissions of ammonia to the environment. Emissions to air and to discharges to sea need to   be l imited and the ammonia loss need to be kept at a minimum.

With respect to HSE, design data and testing ranges, the Chilled Am monia plant will be subject to many of the same design and functionality items as mentioned for the amine plant. Multiple temperature and pressure  measurements in absorber and stripper will be provided to enable establishment of complete mass  and  energy balances. The design will also allow for liquid, gas and solid sampling and pH measurement at feed, exit and intermediate points in the absorber and stripper. The design shall allow for the simulation of the  non  optimal conditions (off set conditions).

The test program for Chilled Ammonia will focus on the following:

• Determination of the ammonia losses from test plant.
• Evaluation of the stripper operating pressure.
• Evaluation of process temperatures on thermal duty and CO₂ capture efficiency
• Assessment of process kinetics for selected operating conditions
• Evaluation of performance of equipment
• Long duration tests of stable operation at industrial conditions.
• Evaluation of sensitivities to flue gas composition (sulphur, oxygen, particles, etc.) .
• Determinatio n of material and corrosion issues.
• Confirmation of operational stability and robustness.
• Evaluation of c hallenges around slurry operation and influence of solids  content.  In  particular,  turn down o peration, process control and operation, fouling and transportability, solid separation.
• Assessment of foaming issues for process.
• Determination of NH₃/CO₂ in rich and lean solvent all ove r the process and evaluate its impact on CO2 capture efficiency and steam consumption.

The activities on the chilled ammonia will progress in parallel with those of the amine plant . Determi nation o f design philosophy, in p articular with respect to scale -up is an important activity before start -up, and will be verified in the test program.

7. Time Scedule

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The investment decision and project approval is planned for end of 2008. It is aimed to have the start -up in 2011. The first test campaigns will start after about some months of comissioning. TCM will be operated for a period o f at least 5 years enabling an extensive validation and development o f the chosen technologi es. More information on future developments can be found on the TCM homepage on the website of Gassnova SF [ 9].

8. Conclusions

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The European CO₂ Test Centre Mongstad will be a n important d riving force in the qualification of large -scale capture technology and development of improved technology. It will establish an international test site for emerging technologies, equipment and solvents, as well as a location suitable for a wide range of research related to  CO₂  capture technology. It will contribute in the search for ways to reduce the CO₂ emissions and to limit the environmental consequences of human activities. This project is unique in the world due to its  ambitions,  its flexibility of CO₂ so urces and technologies, its cooperation of international companies from both oil and power industry and its agreement that initiated the project. We will be “catching our future”!

9. Acknowledgements

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The authors thank the TCM steering committee and the partners Gassnova SF (representing Norwegian State), DONG Energy, Shell, StatoilHydro, and Vattenfall for granting permission to publish this paper. The authors would like to express their gratitude to all current and previous TCM team members.

10. References

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1. Website of Norwegian Government (Norwegian only) , http://www.regjeringen.no/upload/kilde/oed/prm/2006/0143/d dd/pdfv/293147- avtale_mellom_staten_og_statoil_mongstad _12_okt_06.pdf, October 2006
2. Intergovernmental Panel on Climate Change (IPCC), Carbon Dioxide Capture and Storage, IPCC Special Reports, http://www.ipcc.ch/ipccreports/srccs.htm , ISBN-13 978-0 -521 -86643-9, Cambridge University Press, New York, USA , 2005
3. R. Steeneveldt, B. Berger and T.A. Torp, Chemical Engineering Research and Design , 84-9 (2006) 739
4. IEA Greenhouse Gas R&D Program, Improvement in Powe rG eneration with Post -Combustion Capture of CO₂, Report Number PH4/33 , 2004
5. D. C. Thomas (Ed.), Carbon Dioxide Capture for Storage in Deep geological Formations – Results from the CO₂ Capture Project, ISBN 0 -08 -044570-5 (2 volume set), Elsevier, Oxford, UK , 2 005
6. J.N. Knudsen, J. N. Jense n, P. Vilhelmsen and O. Biede, First year operation experience with a 1 t/h CO ₂ absorption pilot plant at Esbjerg coal -fired power plant , Proceedings of European Congress of Chemical Engineering (ECCE-6 ), Copenhagen, 16 -20 September 2007.
7. N. Solie, Chilled Ammonia Process for Post-Combustion CO₂ Capture, Tekna kursdagene , NTNU, Trondheim, 3 -4 January 2008
8. Press release by Reuters, http://www.reuters.com/articl e/pressRelease/idUS225 300+27 -Feb- 2008+BW20080227, Feb. 27, 2008
9. Gassnova TCM homepage , http://www.gassnova.no/, 2008

Collection overview: Research for more than 10 years